The role of triblock copolymers in the bioleaching of chalcopyrite: Electrochemical studies, passivation, and biological compatibility

Hydrometallurgical processing of chalcopyrite is limited by slow dissolution kinetics, mainly associated with electrochemical passivation and the accumulation of secondary product layers. This study investigates the effect of the triblock copolymer surfactant, Pluronic F108, on chalcopyrite shake-flask bioleaching using a mesophilic bacterial consortium over 35 days. F108 showed a clear concentration-dependent effect on the bioleaching performance. At 10 ppm, dissolved copper increased from approximately 220 ppm in the surfactant-free control to more than 810 ppm, accompanied by higher dissolved iron concentrations and higher bacterial counts than high-F108 systems. Electrochemical measurements showed that F108 did not substantially change the initial anodic dissolution response of freshly polished chalcopyrite, indicating that it did not directly catalyze the initial charge-transfer process. In contrast, LPR measurements on aged electrodes and residue characterization by XPS, XRD, and SEM/EDS suggest that low F108 concentrations influenced the longer-term accumulation and morphology of sulfur- and iron-bearing secondary products. At higher dosages (200–500 ppm), bacterial activity and ferric iron generation decreased, resulting in lower copper extraction than at 10–50 ppm. These results indicate that F108 can improve chalcopyrite bioleaching within a limited dosage window, but its benefit depends on maintaining microbial activity while reducing the accumulation of secondary passivating products.